From one aspect, the present invention relates to the use of a damper for controlling the swinging of a pivoted door. There are known dampers which are used for controlling the swinging of a door and which comprise a cam and follower mechanism, the cam being connected with the door to turn with the door and the follower being urged by a spring towards the cam so that the spring is compressed when the door is opened and the spring urges the door to swing towards the closed position. The damper restricts the speed of closing.
A damper which is suitable for controlling the swinging of a door in either of two opposite directions from a closed position is disclosed in United Kingdom specification 852213 published Oct. 26th 1960. The damper disclosed in this specification comprises a housing within a body is guided for reciprocation relative to the housing. Springs urge the body in one direction relative to the housing. A pair of cylindrical chambers are formed in the body, these chambers having respective axes which are inclined to each other and to the direction of reciprocation of the body. Each chamber contains a piston carrying a respective follower which bears on a common cam. The cam is rotatable relative to the housing with an operating member of the damper. Damping action is achieved by restricting the rate at which oil can escape from one of the cylindrical chambers through a respective orifice. The volume of the chambers is small, as compared with that of the housing.
For closing and holding closed large and heavy doors, there is a requirement for a door closer having a strong spring. There is also a requirement to restrict the overall dimensions of the door closer. It is possible to provide a strong spring in a housing of acceptable size. However, it is more difficult to provide an adequate damping action in a door closer having a cam and follower mechanism and a strong spring, if the throw of the cam is restricted by the overall dimensions of the door closer. Typically, the throw of the cam of a door closer having acceptable overall dimensions cannot be more than about 20 mm. To compensate for the limited throw of the cam, it has been proposed to amplify the movement by means of a lever and apply the amplified movement to the damper. An example of a damper incorporating a lever is disclosed in United Kingdom specification 905686 published Sep. 12th 1962. However, this arrangement is not entirely satisfactory. The present invention provides an alternative damper arrangement which is more satisfactory than is the use of a lever.